(1) Field of the Invention
The present invention relates to a recording medium for a sublimation type heat-sensitive transfer recording process.
(2) Prior Art
Sublimation type heat-sensitive transfer recording process have various advantages, including quiet operation, compactness, low cost, and simple maintenance of the recording device. In addition short output time and high gradation recording is easily achieved by changing the amount of thermal energy on the sublimation disperse dye continuously; and high-density and high-resolution recording is also possible.
With these favorable characteristics, sublimation type heat-sensitive recording method are far more advantageous than any other recording method in production. In particular, it is capable of producing full-color hard copies, and it has been extensively used as the recording method for color printers and video printers.
The recording medium for sublimation type heat-sensitive transfer recording method normally consists of a substrate of cellulosic fiber paper or synthetic paper (mainly polypropylene paper), which is coated with a dye-accepting layer. The above substrate, however, has several disadvantages: it tends to curl after being recorded with heat from the thermal head, thereby degrading the transport characteristics of the recording medium in the printer; the curled print-outs also cause problems with respect to handling and filing.
In an attempt to solve the above problems, laminated paper made of cellulosic fiber paper bonded to synthetic paper has been proposed for the substrate, as disclosed in Japanese Patent Application, first publication No.(Tokukai Sho) 62-198497. It is, however, still difficult to totally eliminate curling even with this substrate due to the fact that dissimilar materials of different linear thermal expansion coefficients have been laminated together. Another disadvantage is its increased cost due to the use of expensive synthetic paper made of plastics. Other methods have been proposed to prevent curling; Japanese Patent Application, first publication No.(Tokukai Sho) 63-214484 discloses a substrate of synthetic paper that is lined on the back with a bonded layer of cellulosic fiber paper or plastic film. Japanese Patent Application, first publication No.(Tokukai Hei) 1-44781 discloses a substrate which is coated on the back with thermoplastic resin or a similar material to prevent curling. Each of these substrates, however, tends to be expensive, running counter to the goal of cost reduction.